The plasma membrane of human and rat liver parenchymal and Kupffer cells will be investigated. The proteins in these membranes will be isolated, separated into molecular weight classes and characterized. The arrangement of the proteins in the plasma membrane of these cells will be established using the lactoperoxidase probe system. The plasma membrane of normal adult cells will be compared to that in the fetal liver as well as a variety of hepatomas. The same procedure will be applied to human liver and human hepatomas. In a parallel study the plasma membrane of human lymphocytes will be isolated and the plasma membrane proteins investigated. The plasma membrane of normal lymphocytes from healthy children will be compared with other lymphocytes: those of children with acute lymphocytic leukemia (untreated), cells from children in complete remission and receiving chemotherapy, and lymphocytes from children who previously had acute lymphocytic leukemia and are in continuous complete remission for more than three years and off treatment for at least one year.